Optical memory cards are known. Such cards may be distinguished from electronic or flash memory cards which rely upon non-volatile integrated circuit chips to retain data. Optical memory cards contain laser recording material to contain data, similar to recordable compact disks called CD-R's and may, or may not, also contain an integrated circuit chip. When an optical memory card also contains an integrated circuit chip it is known as a hybrid smart card. Providing security for optical data cards is an important consideration.
U.S. Pat. No. 5,932,865 to Drexler teaches a method for inhibiting the counterfeiting of electronic cash cards by bonding an optical memory stripe to the card, recording optical validation data on a specific location on the optical memory stripe by forming a plurality of spots in a surrounding field of reflective layer, reading the optical data on the stripe by detecting an optical reflective contrast between the surrounding field and the recorded spots and comparing the data to a reference.
U.S. Pat. No. 4,863,819 to Drexler teaches an optical data card comprising a film substrate layer, a highly reflective layer and an optical storage layer with a pattern of clear and partially clear data marks revealing reflectivity in the underlying reflective layer. The reflective layer is highly reflective at a read beam wavelength in the red or near infrared range and less reflective at actinic wavelengths either in the blue/green range or in the ultraviolet range.
U.S. Pat. No. 4,312,938 to Drexler teaches a method for making a broadband laser recording and storage data medium by a stepwise procedure involving normal photographic development of an exposed photosensitive silver-halide emulsion followed by fogging and silver diffusion transfer.
U.S. Pat. No. 4,745,268 to Drexler teaches the use of two optical systems to read visually readable information and laser recorded machine readable information on an information card.
U.S. Pat. No. 4,754,128 to Takeda et al. teaches an optical card comprising a card substrate and a light reflective layer on the card substrate. The light reflective layer comprises an optical higher reflection layer and an optical lower reflection layer. The optical higher reflection layer has an optical information pattern formed.
U.S. Pat. No. 5,300,764 to Hoshino et al. teaches an optical identification label consisting of an area of a hologram or diffraction grating which is transparent to visible light but reflects incident light with a specific reflective directivity. By identifying the reflectivity directivity, it is possible to identify the authenticity of the label and the object to which the identification label is affixed.
The largest users of optical memory cards are governmental agencies. Such cards are used by the Immigration and Naturalization Service (INS) for its Permanent Resident Card, also known as the "Green Card", and by the U.S. Department of State for its LaserVisa card used by Mexican citizens who make frequent visits to the USA. All of these cards use the Drexon.TM. media for laser recording of data, a registered trademark of Drexler Technology Corporation for a silver particle-based material. There is a concern about attempts to counterfeit these optical memory cards using reflective laser recording media other than Drexon.TM. media. Imitation laser recordable materials typically would use either vacuum deposited metal films or laser beam sensitive dyes.
It is the object of the present invention to devise a method and apparatus to inhibit the counterfeiting of Drexon.TM.-based optical memory cards and hybrid smart cards.